Electric furnace.



W. K. UUIH.

ELECTRIC FURNACE. APPLICATION FILED APR.4.YI9I8.

1,299,110. Patented Apr. 1,1919,

2 SHEETSSHEET 2.

/lux/Lmrrv [Leemans lvl/1m ELfCTnoDEs,

Ffm/#cram TERM/NHL 6mp UNITED sTATEs PATENT- WILLIAM K. BOOTH, OF CHICAGO, ILLINOIS, AssIGNon To Boom-HALL' coman?, or

CHICAGO, ILLINOIS, A CORPORATION'OF ILLINOIS.,

ELECTRIC ACE.

' Application led pril 4, 1918.' Serial No, 226,589.l

To all whom it may concern.' p

Be it known that I, WILLIAM K. BOOTH,

- a citizen of the UnitedA States, residing at Chicago, in the county of Cook and State of y the following is a specification.

v This invention relates particularly to elec-l A tric furnaces equipped with wall terminals,

or wall-contacts, adapted tO co-act with electrodes which extend into the heating or fusing chamber of xthe furnace, as shown," for instance, in United States Letters Patent to William K. Booth, No. 1,244,415, granted October 23, 1917. l

The'primary Object of the present invention is to provide an improved furnace con struction of this type, provided with4 an improved wall terminal or terminals.

The invention is illustrated, in its 'pre'-v ferred embodiment in the` accompanyingl drawingsv in' which- Figure 1 represents a plan sectional view of a furnace constructed in accordance with the invention, the section being taken a proximately as indicated at line l-l of ig. 6; Fig. 2, a broken sectional view'taken as indicated at line 2 of Fig. 1; Fig. 3, a sectional view taken as indicated at line 3 of Fig. l, showing the cross-section of the shank of the skeleton grid employed at ythe point where the section is taken; Fig. 4, a 4sectional view of the shank of the gridtaken at line 4 of Fig. 1; Fig. 5, a sectional view taken as indicated at line 5 of Fig. 1 and showing a portion of a radiator Iattached to the shank of t'he grid; Fig. 6, a broken vertical sectional View of the furnace taken at line- 6 of Fig. 1; and Fig. 7, a broken vertical sectional view-taken as indicatedat line 7 of Fig. 1.

In the preferred construction, which is illustrated, A represents the body of a fur-` nace; B and B1 wall-contacts, or wall terminals embedded in the bottom or hearth of thel furnace; C and C1 pairs of grids forming a portion of the wall terminal B; and D and D1, pairs of grids forming a portion of the wall-contact B1'.

The furnace-body A- preferably comprises the usual steel shell 1 provided with a refractory lining 2, in the bottom of which Inthe bottom ofthe shell is la`laye1". 3 of highly refractory` material, sandy l.between the wall-contacts B and B1'is'a'centralwall or bridge 3a of the samefmaterial. ',Thcinner lining- Bbfofthe bottom isof the same highly refractory material, 'and aiords fac'- 'ings for the wall-.contacts Band VB1,-which '.facings become V"conductive when heated.

The portions 3, 3? and 3b ofthe bottom wall form a partof the lining 2 of thegfurnace.

erably comprises ,a metal grid or'grids em- The shell-1 may be lined withrei4 fractory bricks 2b, and the remainder of the 65 l refractory lining may bemoldd in .place if desired, and fused under the action of the`J .electric arc to forma monolithic mass. f11 f"|'`- Each of the wall-contacts B and Blpref-I 70' vare embedded thewall-contacts B .fand B1.. 4 y' bedded in conductive material lof the'secondv If desired, one may take a miXtureOf fractory material or materials, whichfare non-conductive Vwhen cold, and, carbonv powder, with a suitable binder, so as to' comcommodate the wall-contacts, the mixture also belng compacted. in the interstices of the grids. The use of such a -miXture vis pactly fill the spaces or chambers which. ac- Y. f

known in the art, but such amixture may be .v used 1n connection with the improved grids herein shown.

It is preferred however, to forni the bodies of the wall-contacts of a metal carbid, employingthe method fully described and claimed in my co-pending application No. 226,588-fi1ed of even date herewith. Following is a description of the method of forming an acid furnace, which constitutes a modificationV of the construction claimed in my co-pending application mentioned.

According to this method, the portions 3, 3a and 8b of the lining of the bottom of the furnace are composed of silical which is fused by means of the electric arc to form a monolithic mass. 'The layer 3 may first. be formed, and a layer of brick may be placed in the space which is to be occupied by the intermediate wall 3a. I then take a mixture of silica, ycarbon-powder, and a suitable binder, such as coal-tar, mixed hot, and

placca layer of saidmix'ture in the bottin of the space which is to b e occupied by the A Wall-contact, place the grid or grids 1n position, cover them With a'layer of the mix#v carbon to be present in the mixture. One

i sio+2o=si+2co si+o=sid y y vThe temperature should be between 1500 and 2000o C. At this temperature the reactions noted take place, assuming an excess of may' use about 60 per cent. silica, Oper cent. carbon, and just enough coal-tar' or hardroofing-pitch to afford a suitable binder to enable themixture to 'be tamped in place and hold its form until subjected to the fusingaction of the electric arc. ln this action, the

' silicon is set free and instantly unites with the carbon, forming silicon carbid Which cools'as a hard monolithicmass or matrix,

holding the excess carbon and any refractory impurities which may be present. After the first layer of silicon carbid is formed,

4successive layers of the mixture adapted to form the carbid may be tamped in place and subjected to the action of the electric arc to convert the silicon to a carbid, which carries the excess carbon. rfhese masses are Welded together, forming virtually a single monolithic mass. As the operation progresses, and preferably before the carbid' terminals have been formed, the central bricks may be removed and the space filled with silica, which may be fused by means of ,the electric arc, thus building up the central Wall 3a, layer by layer, if desired. After this Wall is built, layers of silica are sintered or fused in place to form the lining 3b, which will become conductive when hot. ln the operation of fusing the materials forming the lining 3b, this lining becomes welded or united to the carbid layer ibeneath, .as Well as to the bridge 32.50 that the Whole hearth of the furnace lconstitutes virtually an integral monolithic mass in which the gridsare embedded. l

In Fig. 6,. E represent electrodes which depend into the fusing-chamber of the furnace and co-act with the Wall-contacts embedded in the hearth. The furnace may be preliminarily heated to render the facings *l 3" of the Wall-contacts conductive in any suitable manner, as for instance, by employ- V ing an auxiliary electrode to cooperate With the main electrodes the manner described in the above mentioned patent.

There are four pairs of grids shown in Fig. 1, tWo pairs forming a part of the Wallcontact B and tWo pairs forming a part.

insane 1 of the yWall-contact B1. `Each pair is like the others, so that a description of one palr will apply to the others. The pair of grids C comprises complemental grids 4 and 5,

vhaving Shanks 4 and 5, which are firmly.

united together by means of bolts 6. The

grids may 'be of any suitable metal, such as v steel, iron or copper. Each; grid is of skele ton construction, `and preferably comprisesv thin bars which are united by other bars extendingrat an angle to the first mentioned bars.

hus the grid et comprises bars 4 united by bars 4c, the bars 4 being extended vShanks La and 5EL is formed With` a. View to avoiding the use of large or heavy'masses of metal, with a .view to overcoming objectionable hysteresis and reactance and skin effects. Thus, the cross-sections of the shanks taken as indicated by the arrows'at i The bolts Which are near the outer ends of t-he Shanks serve to connect with the Shanks the metal-conducting bars 7 Which connect with the bus-bars-or conductors 7, which connect the Shanks of the grids on each side of the furnace, as Will be understood from Fig. 1. Thebus-bar 7 at one side of the vfurnace connects with a conductor 8, which may lead to an auxiliary electrode, and also connects with a conductor 9, which forms a part of the external circuit l0, and which may connect, for instance, with the secondary circuit of transformerl means. The bus-bar 7n-at the opposite side 0f the furnace is shown supported by insulators 11. The circuits of this furnace may be arranged, if desired, in accordance with the circuits shown in Fig. 2 of the patent mentioned above, in which case an auxiliary electrode would be supplied for use in preliminarily heating the furnace, in the Ina-nner described in said patent.

The shank of each grid is equipped at its outer end with a radiator 12, which comprises a iin 12a equipped at its opposite sides Withradiating ribs 12b. A section through the radiator is shown in F ig. 5. The purpose is to cool the shanks by radiating heat to the air, thus ren-dering it unnecessary to Water-cool the grids.

It will be noted that the grids are preferably disposed near the outer portion of the 'bottom Wall of the furnace, so that the grids are protected from the heat in the furnace by the carbid blocks B and B1 and the highly refractory facings` 3b of said blocks. The grids are adapted to make intimate contact with the carbid blocks, and because of l is higlil Ciallyw silicav -In case-the facings Bb'are partiallyI destroyed, thel improved wall-contactsv whichl I preferably carry a-:considerable 4ain oi1nt of free carbon, still offer resistancetodisin? tegration by heat, and will give upl'lessff carbon 'to the metal bath in the furnace thanj would a pure carbon block, for instance,

' barswandf a, A" laminated shank extending through said wall, andv a block of conductive refractory material in which said gridA is eiiibedded.A nection with the wallfcontact, in some cases-.fVv 6. In vthe facing of silica may be dispensed with,

lf desired, the metal grid may be protect-r 'th comparatively lsmall cross-section. of the grid at any, point, objectionable hysteresis v and reactanceand, skin effects are avoided Where alternating currents 'are employed."

VThe silicon carbid blockaffords af com#` paratively good conductor of electricity, and

en protected .by the'facings 3b of;

when employed' asa wall-contact. S

.While it is preferred Ordinarily', a', enr-f ploy afacing of' silicay or other highly'refractory material of acid character, in ooned by a suitable lcoatingor jacket of carbon to prevent fusing or disintegration ofthe grid when the carbid is being formed. This may` be accomplished, for illustration7 by@ dipping the grid inmelted tar containing free carbon, or in melted t-ar and then into carbon powder which will adhere tothe tar."

If a portion of the grid combines with` carbon, this will cause no serious defects so long as sufficient metal is preserved tomaintain the mechanical strength of the grid and avoid breakage, moreover, a sufliciently deepl layer of the carbid-forming material may be placed above the grid to protect it from fus# ing, as it is not essential that these materials Within the interstices of the grid shouldbe converted to carbid.

It may be remarked that the formation of the grids is such as not onlyto avoidl reactance, hysteresis and skin effects, but. also, the grids present a very large area of contact to the conductive body in 'which they are embedded, thereby avoiding injurious .local heating and loss of efficiency in the electric circuit.

The foregoing detailed description' has been given for clearness of understanding only, and no unnecessary limitation should be understood therefrom, but the appended.

claims should be construed as broadly as permissible in vieu7 of the prior art.

What I regard as newand desire to secure by Letters Patent is- 1.`In an electric furnace, a wall-contact comprising a skeleton grid and conductive refractori7 material in which said grid is i embedded.

adapted to extend through a wall of the furresstant 'to disintegration, :espe-` j nece and connect circuit of the furnace.' 1 f. y

` 3. In lan Leltric fiuiiace,I

through a wall.I of the furnace-Q v I' v 'orlcmetal having ashank extending t an electric furnace, a wallfcontact v comprising a body'of conductive refractory v inate'rial, and a` member embedded therein band having a shank extending through the.

furnace-wall and equipped with. anair'radiator. ly

7.' The combinationwitha fu'Hiace-lowlyll having a refractory wall, of a wall-cidad'. comprising silicon carbid forming amenov v lithic mass.. f H -8. The combination with a furnacebody' having a refractoryV wall, lof a wall-contact comprising silicon carbid forming ameno-fz.; `Y

lithic matrix and a refractory conductive material in said matrix. f

4. The combination with a-"fu'rnace-pro-Hy vided with a "refractory wall, of'an open-fy j 75 ugh said-wall, said grid and shank being -coniposed--ofstions ofsinall area. f f5. "lhecomhinati-onjwithv aA furnace havv ing a"Y refractory Wall,l of a lgrid comprising:

9. Iny an electric furnace, a wall-contact: .i

comprising silicon carbid forming a. hard;

matrix, and a yfacing of silica.

10. vIn an electric furnace, avvalbcont'act'l`4 comprising a hard 'mass of` silicon carbid forming armatrix, carbon carried in said ma,

trix, and a facing of silica'.v

11.- InA an electric furnace, a wall-contact comprising a hard mass of silicon -'carbid, a grid embedded-therein and having a shank adapted to `extend through the furnace-wall,

and a hard vrefractory facing forming thel inner lining of the wall-contact,l which becomes conductive when heated, said lining being of an acid character.

12. The method of forming an acid hearth, i

.which consists in mixing materials adapted to react and form a silicon carbid, and subjecting the mixture to a temperature suicient to effectreaction and form a monolithic mass.

13. The method of forming a wall-contact e con carbid, and subjecting the mixture, n i

situ, to a temperature suilicient to effect reaction and form a monolithic mass.

14. The method of forming an acid furnace wallQcontact, which consists in mixing materials comprisingxsilica and carbon, and

subjecting the mixture, to a temperature 1n excess of 1500,o C. in such manner as to cause reaction and form silicon cal-bid in a monolithic mass.

1 5. The'method of forming an acid -furnace with a Wall-contact, which consists in mixing silica and carbonaceous material in quantities suiiicient to furnish an excess of carbon, and subjecting the materialsto the l0 action of an electric arc at such a temperature as to form silicon carbid in a monolithic mass as a matrix carrying the excess carloon.

WILLIAM K. BOOTH. 

